Automatic telephone trunking system



INVENTOR vvmFgED 1'. WELL ATTORNE June 2, 1925. w. T. POWELL AUTOMATIC TELEPHONE TRUNKING SYSTEM Pm W M 6 Haw QM @Q ms Patented June 2, 1925.

UNITED sures 1,540,418 PATENT crrlcs.

wrnrann r. rownnn, or Rocnusran, new roan, nssreuo Te THE CARLSON TELEPHONE na vurno'ruanvo oonrnny, or 3,

ooaronnrron OF NEW YORK.

mo ume- NEW YORK, 4

AUTOMATIC TELEPHONE ru-unxrlve s-YsrnM.

application fil d Aug t 1918. Serial No.'250,617.

To all whom it may concern:

Be it kn n tha l, W NF ED T, OWELL, a citizen of the United States, residing at Rochester, Monroe County, New York, have invented new and useful Improvements in Automatic Telephone Trunking Systems, of which the following is a specification.

My invention relates to improvements 1n automatic telephone systems and more particularly to an improved construction in non-numerical trunking switch line circuit for use in such a system. i lVhile my invention in some of its aspects is of a broad nature: and may be appl ed to a line circuit using switches of various con struction, I prefer a forinof my invention wherein use is made of a line switch, the

wipers of which rotate in butone direction.

It is an object of my invention to provide a switch circuit arranged to provide for the traveling line switch with which it is associated, alternate home and trunk point resting positions, the trunk point resting positions being the positions in which the line switch may make connection between the line with which the switch is associated and the trunk circuit and the home point positions being positions wherein theline switch may come to rest after the release of a connection between the associated line Oil? cuit and the trunk circuit. In the operation of the system of my invention I so organize the apparatus thereof that immediately following the release of a connection through contacts of the line switch the line switch will immediately traveltothe next home point position, the home point positions and the trunk point positions of the switch being preferably alternated although it is apparent that several trunk point positions may be interposed between successive home point positions, and conversely if desired, a plurality ,of home point positions may be interposed between suc.-,

cessive trunk point positions. I am aware that line switch systems have been provided in which a single home point is provided for the switch to which home point the switch rotates in either one or the other div rection after the release of an established connection. I am likewise awarethat other line switch systems have been provided wherein the line switch does not travel after the release of an established connect on "but 'ble have whenthe line isa ren ains withits wipers in contact'with the last connected trunk contacts. w I Among the objects of myinvention are the securing of the following advantages Over the aforesaid .line switch systems'of the art.- The line switch circuit of my invention is simple. It contains few parts, such parts being positive in operation and may he cheaply constructed and easily maintained in operation. a a

It is a further object of my invention to eliminate the necessity of such expedients as slow acting line relays which give troum --practice since slow acting line relays, do not operate with the same speed on line circuitsofidifferent resistance.

Another object of my invention is: the provision .of a system in which mechanical interlocking of the line circuit relays are not necessary. to cause ardifferent kind'of operation of one of the relays when the line is a called line from that which'it would calling line. ()ther' objects of my invention and the invention itself will be apparent as the description thereof progresses. Referring to the figure accompanying this specification at A, I show a telephone sub-station located a cut off relay (10.1%. and line relayL. R.

and stepping magnet S. M., the said step ping magnet being" arranged in the wellknown manner to step the line switch wipers from. one position to another, the step oing preferably being accomplished on :the hack stroke of the armature of the stepping magnet S. M.

The line switch wipers are-four in number, 111 and 123 being the line wipers which are provided for the purpose ofextending the circuit of the line to thetalking com ductors of a trunk circuit such as the trunk circuit'H. lVipers' 112and 122 are pro,- vided for the purpose of controlling cir cuits local to the exchange as will be later ribed. All of the four wipers ofa line v s eh which is individilial to a line suchas a line L are preferably mounted on a rotatable shaft, each adapted to successively engage contacts arrangedin a circular row the alternatesetsof contacts suchas the set comprising theicontacts 1185114} 141 142 and the set of contacts comprising the contacts 115, 116, 126, 127, being what I term home position contacts and upon one of which sets of contacts of the plurality provided for the purpose the switch will come to rest 'afterthe release of a connection previously established over one of the intermediate sets of contacts which I call trunk position sets.

The subscribers? station A is of any suitable or approved type and comprises the usual receiver 2, transmitter 3, switch hook 4, ringer 5 and condenser 6. Being an automatic sub-station it is also provided with an impulse transmitter or calling device, which is here represented by a pair of impulse springs 7 and 8 and an impulse wheel 9, which latter is assumed to be controlled through the medium of a finger hole dial (not-shown) in such a manner that the impulse springs 7 and 8 may be momentarily separated a number of times, corresponding to the digit called.

The illustrated connector switch H is of I switch comprising the wipers 30, 31, 32 and 38 is controlled by'the private magnet 84 in the usual well-known manner. 35 is the usual release magnet. The opera; time of the switch are controlled through the medium of the double wound line relay 86, through which the calling subscriber receives talking current. The called subscriber receives talking current through the so-called. back-bridge relay 37. The ringing relay 38 is the means through which ringing current is applied'to the called line.

The substation A and the'line switch L, S are similar in all respects to the substation Aand the line switch L. S.

For the purpose of supplying battery current for operating the central oflice apparatus, and for talking purposes, there is shown a battery 13 having one terminal grounded at G. The busy signaling mae chine, L, as represented herein, comprises an induction coil or transformer, the primary winding of which is includedin a local circuit with a battery and an interrupter. Through the medum of this interrupter an intermittent current is supplied to the primary winding which induces an alternating current in the secondary winding, whereby when said winding is conne'ctedw'i'th the The The magnet,

subscribers line, a buzzing sound is heard in the receiver. i

Having given a general description of the apparatus involved in the system, and in order to give a complet understanding of my invention, I will now describe how the subscriber at substation A may call the subscriber at substation A. By the removal of the receiver from the switch hook at the substation preparatory to making a call, an energizing circuit is closed through the line relay'L. R. of the line switch L. S. This circuit extends from ground through normal contacts of the cut off relay C. O. R. over the line conductor 42, through the substation A, line conductor41, normal contacts of the cut ofirelay 0.0. B. through the winding of the line relay L. R. to negative battery Band thence to ground at G. The line relay L. R, upon venergizing, operates to close the circuit of the stepping magnet S. M. At the time the call is initiated the line switch wipers 111,112, 122 and 123 are in the position shown in the drawing, namely, upon different contacts of a set comprising homepoint contacts such as the home point'contacts 113, 114, 141. and 142.

All of the home point contacts in the second row of the contacts and adapted to be engaged by-the line switch wiper 112, are connected together by a circuit conductor which is also connected through normally opened contacts 121 of the line relay L'.' R. to ground. Thus whenever these normally opened contacts 121 are operated, ground is placed on the alternate home point contacts for the purpose of operating the stepping magnet should the line at the time be a calling line. At this time therefore ground placed upon the home point contact 114 by the operation of the line relay contacts 121 will complete a circuit including the said contacts 121, the wiper 112, home point contact 114, normal contacts 132 of the out 01f relay G. O. R. throughnormal contacts of the stepping magnetS. M. which contacts are adapted to be broken whenever the steppingmagnet is energized, the circuit continuing throughv the winding of the stepping magnet S. M. and thence to the negative pole of the source of current B.

Current from the said source flowing over this circuit the stepping magnet S. M. will energize and will attract its armature thus breaking its own energizing circuit. This will cause its armature to be again retracted according to the well-known principle of any operating direct current buzzer, and the stepping" magnet armature arranged in the well-known manner upon'being retracted to advance the line switch wipers one step forward along their respective rows of contacts. When the first step is thus made-if the wiper 112 which may be called thetest wiper finds the next] succeeding contact 113 "without a ground connected to it the operation of the stepping magnet will cease since its circuit conductor leading. to ground through normal contacts 132 of the cut off relay C. O. R. willbe broken but we will assume in this description that due to the fact that the trunk circuit whose incoming terminals are connected to the contacts 117, 118, 12 1' and'125 as well as to multiples of these contacts on the diiferent line switches ofthe group of the lines served by the group of trunks is a busy trunk circuit, that is, it has been seized for use by another line switch of the group and that therefore, in a manner which will later be made apparent, a connection will therefore he had to all of the test contacts 118 of this trunk circuit to the ground pole of battery that this ground will serve to cause the stepping magnet to continue to step the wipers of the line switch to succeeding contacts. 1 I

The substituted circuit for the stepping magnet may be traced from ground placed on the test contact 118 by the operation of apparatusactuated by virtue of the connection existing between the trunk circuit whos terminals are connected to the set of contacts 117, 118,124 and 125 and a connected line circuit, contacting wiper 112normal contacts 132 of the cut off relay 0. O. K. through normal contacts and the winding of the stepping magnet S. M. to the negative pole of the battery'B. Current flowing from the said battery will again operate the stepping magnet to'p'ropel the line switch wipers to the next set of contactswhic'h'is .an'alternate set of home point contacts 115, 116, 126 and 127, whereupon, the stepping magnet will be again operated to step line switch wipers in themanner described for the first stepping thereof, 'a circuit for the stepping magnet being again traced through normally opened contacts 121 of the operated line relay L. R. through the test contact 116 and the test wiper 112so that the stepping magnet being again energized and automatically retracted "in the manner previously described will cause the lineswitch wipers to occupy the fourth illustrated position bringing them into contactwith the set of contacts 119, 120, 128 a'nd'129 which are connected to an id'letrunkcircuit such as the illustrated trunk circuit'H.

Due to the idle condition of this trunk circuit no ground will be connected to the test contact 120"thereof and the circuit to ground for the stepping magnet S. M. will be interrupted and the stepping magnet will cease to operate. 7 y

While the line' switch was-stepping and prior to the time that-thewip'er's 112' and 122 came into contact with contactsof an not operated forthereason that when the wipersl-IQ and 122 were on home point conground will b found upon both of. these contacts being placed on the test contact upon whichthe wiper 112 rests by the closure of contacts such asthe contacts 13- of thec'ut off relay, such as the cut off relay (1. O. R. of such another line circuit as may at the time be connected to the busy trunk. The closureof such contacts 133 placing ground through its associated wiper like the wiper 112 of the line switch circuit being described upon the multipled test contact of the trunk circuit at the time occupied. Groundis also placed upon the contact upon which the wiper 122 at the time rests by the operation of apparatus in the busy t-PUnl-f circuit which is organized like the trunk circuit H and in such anorganization the circuit to ground from the contact referred to would be tracedvfrom the said contact" corresponding to the contact 128 of the trunk circuitH through be normal coir tacts 151 and through normally closed 0011- tacts 152 of the release magnet 35, thus at such a timewhen the line switch wipers of the line switch; LQS. are traversing the contacts of such a busy trunk :circuit, ground being found upon. both of the wipers 112 and 122 will effectually short circuitthe cut off relay C; (IR. to preventits operation.-

Nowassuming that the stepping magnet has caused the wipers to encounter contacts" of an 'id'le trunlr circuit and in the manner above described has ceased to operate, the: cut off relay G. O. R. will be operated, the circuit forthe operation of the cutoff relay maybe traced as follows. From the negative pole of the source of current B through relatively low resistance winding of the stepping magnet S; M. through the .uor-' mal contacts of the said stepping {contact through 'the'relatively high resistance windingofthe relay CLO. through the line switch wiper 122 trunk contact 128 of the idle trunk circuit through the winding of thespecial slow releasing relay-153 and thence {through normal contacts 152 of thev release 'magnet'35 to' the ground" pole otthe source of current. Current from the said source flowing over this circuit will'operate the relatively high resistance 'relayQ- O, .R. to cause it to attract its armatures but the flow of current through this circuit due to the high resistance of the relay 0. O. R.

will be insufficient to cause the stepping v being operated willclose its contacts 133 to idletrunkcircuit the cut ofirelayC 0. Ris

tacts 132 being opened to prevent further stepping of the stepping magnet.

The first and second armatures likewise being attracted will open the circuit of the line relay L. R. and the connection to ground respectively to clear the line strands and to retire the line relay which will open its contacts 121. These armatures being operated will also cause a closure of the contacts 131 and 130 respectively to extend the circuit of the line conductors 41, and 42 through the lin wipers 111 and 123 and coperating contacts 119 and 129 of the trunk circuit H to the talking strands of the trunk circuit H.

A circuit is now completed including the said line conductors and the substation instrument at A including tandem windings of the impulse relay 36. the said windings being directly connected to the trunk circuit talking strands, and the supply of talking battery to the transmitter 3 of the substation A being supplied through these windings which afford as well an impedance bridge-across the talking circuit so that talking currents will not be unduly diverted through these windings. 1

Current flowing through the windings of the relay 36 will operate it and cause it to close its contacts 5253to operate the. slow-releasing relay 50, the circuit for the slow-releasing relay being traced from ground G throughthe said contacts 52-53 through the winding of theslow relay to the negative pole of the source of current. The relay 50 will be thereby operated attracting its armatures toclose'contacts'54 and 56 and to open contacts 57.

The slow releasing relay 153 having been operated as before described will close its contacts 154 to cause a conductive bridge, of the line strands to be made and to thereby hold the relay 36 operated or to operate the relay 36 should'the subscriber A retire his instrument from the lineat the moment or preceding the seizureof the trunk circuit H by the. line switch wipers. and, to provide that in such a case that a release be caused of the connection existing between the line switch circuit and the trunk circuit. This release will be effected as follows.

The relay 5() being operated attracting its armatures and closing contacts 54 and 56 as before described, the closure of the contacts 5A will short circuit the slow relay 153 which will slowly retract its armature and after a period open its contacts 154. At 7 this time assuming the subscriber hasretired his instrument, the relay 36 will retract its armature being a fast operating relay opening the circuit of the slow releasing relay 50 which will-fora time hold its armature attracted andthe. relay 36 will restore its normal contacts 5152 a circuit thereby being closed for the primary stepping magnet 28-including the winding of the slow releasing change-over relay 61, the circuit being traced from the ground pole of bat-teryt-hrough contacts 5251 of the relay 36 through now mad e contacts 56 of therelay 50,'the winding of the slow releasing relay 61, the winding of the primary stepping-magnet 28 through first position contacts of the side switch wiper 30 to the negative pole of the course of current.

Current from the said source will operate the slow releasing relay 61 and the primary stepping magnet 28 and the switch carriage will be advanced, say in a vertical direction one step. This will close the OE normal contacts 151 which will maintain the short circuiting of the slow releasing relay and maintain the contacts 154 opened thus if the subscriber instead of retiring,

had remained on the line, the conductive bridge across the talking strands would be removed and the talking currents would not be shunted.

However assuming that the subscriber has retired, as before stated, after an interval the slow releasing relay 50 will retract its armature, closing contactsin the release-cm cuit of the release magnet 35, it being understood that the offnormal switch contacts 87 and 93are operated to close these contacts at the same time that off normal contacts 151 were likewise operated by the stepping of the switch. This circuit is traced as follows.

From the ground pole of the,.source of current through normal contacts 5251 of the impulse relay 36, normal contacts 57 of the slow releasing relay 50 which is nowrestored, off normal contacts 87 which are now closed, through the winding of the release magnet 35 to the negative pole of the source of current. Current from the said source operating the. said release magnet will cause the restorationjof the switch carriage and at the same time functioning as arelay, will cause the closure of contacts 155 to place ground potential upon the multiple'd test contact 120 of the trunk circuit and will open the contacts 152 in the circuit to ground leading to the holding contacts 122128 in the circuit of the cut off relay C. O. R. before traced, to release the cut off relay of the line. q k

The cut off relay'being released will retract its armatures and the lower armature being retracted will open contacts 133 and close contacts 132 which last named contacts are in the stepping-circuit of the stepping magnet SLM. The circuit of the said. steppingmagnet is now completed, being traced from ground through now closed contacts155 of the release magnet 35, testeontact 120, line switch wiper 112, now closed contact 132 of the cut off relay, normal contacts and the winding of the stepp ing.ma2'

net lif. tothe negative pole of'the source of current. The current from the said source will energize the stepping magnet to cause it to attract its armature which will cause it to break its own circuit in the manner previously described and upon such breaking will cause the advance of the'switch wipers of the-line'switch one step carrying the switch wipers oii the contacts of the previously occupied trunk circuit H and on to the next succeediugho'me point contacts. i i

There being no ground however on the home point contact which the switch wiper 112 next encounters, due tothe fact that the line relay L. R. is'not at the time'operated, the circuit of the stepping magnet is interrupted and ceases to operate to step the switch wipers, leaving them restii'ig'upon the said next succeeding home point con tacts.

p In the meantime the switch mechanism of the trunk circuit switch H has been restor ingto normal and when fully restored the oil normal contacts 87 are broken to open the circuit of the-release magnet '35 which will restore its contacts to normal position. The other off normal contacts 93 and 151 arealso restored to normal open position and the circuits controlled thereby are restored to normal. 1

Assuming, however, that the calling subscriber remains on the line, he may now operate his calling device for the first digit 2 of the called number, whereby the substation impulse springs 7 and 8 are operated twice momentarily, each time breaking the circuit of the connector line relay 36. The relay 50 oi the connector being slow acting does not de'energize during the momentary interruptions ofits circuit by theline relay 36, and consequently each time the latter deenergizes, an impulse is transmitted through the vertical magnet 28. This circuit extends from ground G through the contact of springs 52'and 51, springs 57 and 56, relay 61, vertical magnet 28 and the side switch wiper 30 (in first position) to the battery B. 'The verticalmagnet 28 receives two impulses over this circuit and operates toraise the switch wipers 25, 26 and 27 to a position opposite the second level of bank contacts. The relay 61, which is included in series with the vertical magnet, remains energized during the entire time that impulses are being transmitted through it and operates to close the circuit of the private magnet 34. The circuit for theprivatemagnet 3-1 extends -from ground G through the contact of springs 62 and c4 and the said magnet to the battery B. Atterthelast impulse is delivered, the relay 61 opens the circuit of the private magnet 34 which, upon deencrgizmg, perm1ts the s de switch to ad- Vance from first 'to second position. The

movement of the side switch wiper 30 from first to second position transfersthe battery connection fromrthe vertical magnet. 28 to the rotary magnet 29.

The calling subscriber now operates his c'alling device for the last digit 0, in'response to which the connector line" relay operates to transmit ten impulses through the rotary magnet 29 in series with the re- 34 to advancethe side switch one more position, i. e., from second to third position. By the engagement of the side switch wipers 32 and 33 with their third-position contact points, the connection is completed. with the called substation, and by the engagement of the side switch wiper 31 with its thirdposition contact point a circuit is established for the cut-off relay winding 67 of the line switch C" as well as for theslow relay "70. The circuit for the cut-off winding 67 8X tends from ground G through the side i switch wiper 31(in third position), private Wiper 26, conductor 68, and the cut-off Winding 67 to the battery lead 100, through the low resistance Winding of the line stepping magnet S M of the called line L S. The called line cutoff relay 67 will be energized to break the circuit of the line relay 7 Othereof andground at GE, but since the line wipers ofthe called line switch restupon the home point'contacts to which no conductors are COI1I18CtQ(l,tl1 closure of the contacts 201 and 202m their circuit, will be without effect. The line switch wiper 203 will likewise be functionless, as it will be resting upon a home point contact to which nothing is connected. A guarding ground potential is supplied to the connector private bank contact 71 of the called line which prevents the same' from being seized by some other connector switch. By the engagement of the side switch wiper 30 with its third position contact point, the circuit of the ringer relay 38 is closed. This circuit ex tends f om ground Gr through the interrupter 72, relay 88, contact of springs 73 and the side switch Wiper 30 (in third position) to the battery B. The ringer relay disconnects the calling line from the called line and bridges the ringing current generator R across the called line to signal the called subscriber. The ringer relay is energized only intermittently through the medium of the interrupter 72. Upon'the response of the calledsubscriber, his line is provided'with talking current through the windings of the back-bridge relay 37, which relay, upon energizing, closes the circuit through the ringer cut-off relay' 74. The said circuit extends from ground G through theside switch wiper 31 (in third position), contact of springs 75 and the said relay 74: to thebattery B. The relay 74, upon energizing, interrupts the circuit of the ringer relay 38 at the springs 73 and closes a locking circuit for itself through the springs 7 6 independent of the springs 75. After the conversation is completed, the connection isreleased by hanging up the receiver at the calling substation in the following manner: WVhen the receiver at the substation A is restored to the switch-hook, the separation of the hook switch springs destroys the energizing circuit of the connector line relay 36. The relay 36 is thereupon deenergized and opens the circuit of the relay 50. The relay 50, upon ,deenergizing, completes a circuit extending from ground G through the contact of springs 52 and 51, springs 57 and 58, off-normal springs 87 and the release magnet tothe battery B. The magnet,

upon energizing, restores the switch shaft and side switch to normal position and its own circuit is broken at the off-normal springs 87 when the shaft reaches its lowest position.- The relay 50 upon deenergizing, also opens the holding circuit for the winding of the calling line out off relay C. O. R. at the springs contact 54. This will complete the circuit of the'ste pping magnet S. M. of the calling line through the lower normal contacts 132 in its circuit, and through'wiper 112, contact 120 ofthe trunk circuit and contact 155 of the release magnet 35; this circuit being completed to ground through contacts of the said release magnet and to battery connected to the opposite side of the stepping magnet S. M. The contacts 155 are closed while the connectorswitch is returning to normal, by the energization of the release magnet 35 whose circuit has been above traced. I

The stepping magnet S. M. of the'calling line having its. circuit closed as before described, will step the wipers 111, 112, 122 and 123 of the calling line switch to the next position and out of contact with the contacts 119, 120, 128 and 129 of the connector switch-H, the said next position contacts being homepoint contacts, since as before related, the home point contacts and the trunk point contacts alternate in the switch construction herein illustrated and described.

The connector switch returning to-normar opens the circuit of the cut-off relay winding 67 of the called line, by the opening of the wiper 26of the connector switch and private contacts 71 of the called line, co-

.- operating therewith, thus retur i :the

apparatus of the called line to normal position. 1

While I have illustrated my invention in connection with one particular type of automatic system, it will, of course, be under- ,stood that it is capable of use With many other forms of systems and is equally as well adaptedfor use in connection with semi-automatic s vstemsthat is, systems in which a manual link circuit is employed in combination with automatic means for establishing a connection between two subscribers lines.

lVhat I claim is 1. In a telephone system, the combination with a line switch, a line relay therefor, a plurality of sets of stationary contacts for the said line switch, each of the said sets of contacts being connected toa trunk line circuit, sets of home point contacts for the said switch, one of the said sets of home point contacts being interposed between adjacent sets of trunk point contacts, line switch wipers, meansto cause the said line switch wipers to move from a contacting set of home point contacts,under the control of the said line relay, means-to cause the said line switch wipers to move from a busy set of trunk contacts, said first-named and said lastnamed moving means including a motor magnet for the said switch, and means associated with each of the said trunk circuits responsive to the idle condition thereof, to disable the said motor magnet to stop the said switch wipers upon its 'set of contacts.

2. In a telephone system, the combination with a line switch, a plurality of stationary contacts for the said line switch, each of the said contacts being connected to a trunk line circuit. home point contacts for the said switch, each of the said home point contacts being separated from the next home point contact by one of the said trunk point contacts, 'a line switch wiper, means to cause the said line switch wiper to move from a contacting home point contact, means to cause the said line switch wiper to move from a contacting. busy trunk contact, said first-named and said last-named -1noving means including a motor magnet for thesaid switch, and'means. associated with each 'of the said trunk circuits responsive to the idle condition thereof, to disable the said motor magnet.

3. In a telephone system, the combination with a lineswitch, a plurality of stationary contacts for the said line switch, each of the saidcontacts being connected to a trunk line I circuit, home point contacts for the said switch, each of the said home point contacts I being separated from the next home point contact by one of the said trunk point. contacts, a line switch wiper, means to cause the said line switch wiper to' move from a contacting home point contact, means to cause the said line switch wiper to move from a contacting busy trunk contact, said first-named and said last named moving means including a motor magnet for the said switch, means associated with each of the said trunl-r circuits responsive to the idle condition thereof, to disable the said motor niagnet, a cut-off relay for the said switch, said last-named means including means for serially connecting the relatively high re sistance winding of said cut-'oii relay in series with the winding of the said motor magnet.

a, In a telephone system, the combination with a line switch, a plurality of stationary contacts for the said line switch, each of the said contacts being connected to a'loca'l con-"- ductor o'la trunk line circuit, associated con tacts for each local conductor contact, each associated contact being connected to a tallo' ingconductor of a trunk line circuit, a pair of line switch wipers for said line switch, means to progressively move the said pair of line switch wipers from a contact of the busy trunk set oi contacts, home point sets of contacts for the said switch also adapted to be traversed by the said pair of wipers,- each set out home point contacts being separated t'rom the next home point contact by a set of the said trunk point contacts, means to cause the said pair of wipers to move from acont-acting home point contact, a line relay for the said switch,- said last-named moving means including a motor magnet and contacts of the said line relay, said first named moving means including the said motor magnet and the said local conductor of the said busy trunk, and means associated with each of the said trunk circuitscon trolling the circuit of the said conductor, to disable the said motor magnet.

5. In a telephone system, the combination with a line switch, a plurality of pairs of stationary contacts for the said line switch, each of the said pairs of contacts being associated with a trunk line circuit, one of the contacts of each pair being a local contact and the other being a line contact of their associated trunk circuit, a motor mag net for the said switch, a pair of line switch wipers, intervening pairs of home point contacts between all ofthe said trun'k point contact pairs, controlling contacts and source of current adapted tobe connected to a contact of the home contact pairs by apparatus of the calling line with which the said line switch is associated, to cause the said motor magnet to move theline switch wipers from a contacting pair of homepoint'contac'ts, and means associated with each of the said trunk circuits and responsive to the busy condition thereof,- to alter the electric potentialof a contact of its associated line switch contact pair, and means responsive to such altered potential to cause the saidmotor magnet to move the said pair of wipers from their contact- 'ing position with the said pair of busy trunk line contacts.

6. In a telephone system, the combination with a line switch, a plurality otpairs of stationary contacts for the said line switch, each of the said pairs of contacts being associated with a trunk line circuit," one of the contacts of each pair being a local contact and the other being'a line contact of their associated trunk circuit, a motor mag net for thesaid switch, a pair'of line switch wipers, intervening pairs or home point contacts betweenall of the said trunk point contact pairs, controlling contacts and aso'urce of current adapted to be connected to ,a: contact of thehome contact pairs by apparatus of the calling line with which the said line switch is associated, to cause the said motor magnet to move the line switch wipers from a contacting pair of home pointcontacts, means associated with each of the said trunk circuits and respon sive to the busycondition thereof, to alter the electric potential of a contact of its asso-' ciated line switch contactvpair, means responsiv'e to such altered potential to cause the said motor magnetic move the said pair otwipers from their contacting position with the said pair of busy trunk line contacts, said means associated with each of the said trunk circuits being responsive to the idle condition thereof, to disable the said motor magnet, to stop the said switch wipers upon its pair of contacts.

7. In a telephone system, the combination with telephone lines thereof, line switches for each of the said telephone lines, a plurality of stationary contacts for each of the said line switches, one of the contacts of each line switch being multiply connected to a terminal of a trunk line circuit, an other of the said contacts of each line switch being multiply connected to a different trunk line circuit, a home point contact for each line switch, arranged before the said trunk line contacts in one of the switches, an additional home point contact being arranged between the trunk line con tacts o'n the said switch, a line switch wiper for each of the said switches, means to cause the said line switch wiper to move from either home point contact upon which it rests,the said' means being responsive to the calling condition of its associated tele-' phone line, means to cause the said line switch wiper to "move from a contacting busy trunk line contact, said first-named and said lasanamed moving means including a magnet for the said switch, and means associated with each of the said trunk cir cuits responsive to the idle condition thereof, to disable the saidniagnet,

'8; In a telephone system, the combinationinc with telephone lines thereof, line switches for each of the said telephone-lines, a plurality of stationaryicontacts for each of the said line switches, one of the contacts of each line switch being multiplyconnected to a terminal of a trunk line circuit, another of the said contacts of each line switch being multiply connected to a different trunk line circuit, a home point-contact for each line switch, arranged before the said trunk line contacts in one of the switches, an additional home point contact being arranged between the trunk line contacts on the said switch, a line switch wiper-for each of the said switches, means to cause the said line switch wiper to move from either home point contact upon which it rests, the said means being responsive to the calling condition of its associated telephone line, means to cause the said line switch wiper to move froma contacting busy trunk line contact, said first-named andsaid last-named moving means including a. magnet for the said switch, means associated with each of the said trunk circuits responsive tothe idle condition thereof, todisable the said magnet, the said last-named means including contacts for serially connecting a relatively high resistance winding of the said cut-off relay in series with the said magnet.

9. In a telephone system, the combination with a telephone line, a line switch there for, a plurality ofstationa'ry trunk contacts for the said line switch, a plurality of home point contacts for the said line switch in-v terposed between the said trunk contacts, a line relay for the-said line, a motor magnet for the said switch, means to cause the motor magnet when operated to move a switch wiper of the said switch from switch point to switch point, acircu-it including a source of current bu energize the said mo- I tor magnet, said circuit includingvnormally open contacts of the said-line relay, the said line switch wiper and the said motor magnet, a cut-off relay for theline adaptedto disable the said line relay,- an energizing circuit for the said motor magnet including the said switch wiper, a contacting trunk point contact, and controlling contacts operated responsive to the busy condition of the said trunk circuit, both of the said energizing circuits for the said motor magnet excluding the winding of the saidzcut-ofi' relay, and a shunting circuit for said outoff relay, the said shunting circuit including the said line switch wi-per..

10. Ina telephone system, the combination with a telephone line, a line switch therefor, a plurality of stationary contacts for-the said line switch, thesaidstationary contacts being arranged in sets, each set of stationary contacts being connected to trunk line terminals, a motor magnet for the said line switch. adapted. to adva ce the wipers position for the saidline switch, a holding circuit for the said line switch, said holding circuit comprising n an established connect1on,a wiper and a trunk line of the said line switch, a releasing mechanism associated with the said trunk circuit adapted to disable the said holding circuit, means to start the said releasing mechanism to operating whenever an idle trunk circuit is seized by the said line switch to interconnect a calling telephone line to the terminals of the said idle trunk line, and a relay for the said trunk line circuit responsive to the busy condition of the said line,to disable the said releasing mechanism.

11. In a telephone system, the combination with a telephone line, a line switch therefor, a plurality of stationary contacts for the said line switch, the saidstationary contacts being arranged in sets, each set of stationary contacts being connected to trunk line terminals, a motor magnet for the said line switch adapted to advance the wipers of the line switch over the said stationary terminals, means responsive to the idle condition of a trunk line to cause the said motor magnet to be stopped when the line switch wipers are brought into contact with the said idle trunk line contacts, a normal position for the said line switch, a holding circuit for the said line switch, said holding circuit comprising in an established connection, a wiper and a trunk line of the said line switch a slow releasing mechanism associated with the said trunk circuit adapted to disable the said holding circuit, means to start the said slow releasing mechanism to operating whenever an idle trunk circuit is seized by the said line switch to interconnect a calling telephone line to the terminals of the-said idle trunk line, and a relay for the said trunk line circuit responsive to the busy condition of the said line, to disable the said slow releasing mechanism. c i

r 12. In a telephone system, the combination with a telephone line, a line switch therefor, a plurality of stationary contacts for the saidline switch, the said stationary contacts being arranged insets, each set of stationary contacts being connected to trunk lineterminals, a motor magnet for the said line switchadapted to advance the wipers ofthe linecswitchoverthe said stationary terminals, means responsive to the idle condition of a trunk line to cause the said motor magnet tobe stopped when the line switch wipers are brought into contact with thesaid dle .trunkil ne conta ts, a n rmal means to start the said slow releasing mech anism to operating whenever an idle trunk circuit is seized by the said lin switch to interconnect a calling telephone lineto the terminals of the aid idle trunk line, and

quick ope 'ating means for the said trunk line circuit responsive to the busy condition of the said line, to disable the said slow releasing mechani m- 13. In a telephone s stem, the combination with a calling te ephonoline, a line switch therefor having a line'wiper and. holding circuit wiper,:"1neans tocaus'e the said line switch to engage the line contacts 01' a non-busy trunk circuit, a normal position for the saidline switch, meansto advance the said switch 15110 11. the said idle trunk circuit contacts to the said normal position, the said means including slow operating mechanism in a connected idle trunk circuit, and a quick operating mechanism in the said trunk circuit responsive to thebusy condition of a connected line, to disable the said slow operating mechanism.

14. In a telephone system, telephone lines arranged to initiate and receive telephone calls, a switch for the use of a telephone line, each switch being provided with home contacts and trunk contacts, said home contacts being interspersed between said trunk contacts, trunk lines terminating in said trunk contacts, means for advancing a line switch to a trunk contact when its telephone line initiates a call, and means maintaining said switch on a home contact when its telephone line receives a call.

15. In atelephone system, telephone lines arranged to initiate and receive'telephoue calls, a switch individual toeach line, each switch being provided with home contacts and trunk contacts, said home contacts being interspersed :between said trunk contacts, trunk lines terminating in said trunk contacts, means for advancing a line switch to a trunk contact when its telephone line initiates a call, means for maintaining said switch on a home contact when its telephone I a line switch when idle, means for releasing a selected trunk, a d means. for moving the operated switch to ahome conta t when the:

selected. trunk is released, a

1?. In a telephone, system, a line, a trunk selecting switch individual to theline comprising a series of contacts some of which, are home contacts and others are trunkcon tacts, said home contacts being scattered among said trunk contacts, a contactianoaadapted to. engage with saidcontac s, and means for normally maintaining said arm in engagement with a home contact.

18. In a telephone system, an incoming line, a'p urality of outgoing lines, a sin tell for interc nne ting said incoming l ne with any of said outgoing lines,v ahold ng circuit completed on the seizure ofc ient said out going lines, means in said holding circuit for temporarily bridging together the two sides of a seized outgoing circuit, means, responsive to said operation for initiatingthe release of said seized outgoing circuit",'anr1 other means normally effective to prevent said releasing operatiorn 19. In a telephone system, an incomil'ig line, a plurality of out oing lines, a switch for interconnecting sai incoming line with any of said outgoing lines, an impulse relay connected to one side of each outgoing line,

a holding circuit for said switch completed on the seizure of an outgoing line, a slow releasing relay in said holding circuit, means controlled by said slow releasing relay for closing the operating circuit of said impulse relay independent of said incoming line, means responsive to theoperation of said impulse relayfor' initiating the release of said outgoing line, and other means including a second energizing circuit for said impulse relay extending through said incoming line for preventing said releasing operation. o

20. In a telephone exchange system, a telephone line, a line switch connected thereto, a normal terminal for said switch, test terminals associated with said switch, a test brush engaging said normal terminal, a relay operated upon the selection of said switch, electromagnetic means energized upon operation of said relay over a circuit through said test brush and terminals for stepping said brush from normal until an idle trunk is found, and other electromagnetic means energized upon the finding of an idle terminal for extending said line, and a circuit independent of said other electromagnetic means and including the first named electromagnetic means for returning said switch to engage said normal terminal.

21. In a telephone exchange system, a telephone line, a line switch connected thereto and automatically operated to seize an idle trunk upon initiation of a call, a selector switch to which said idle trunk is connected, means at sald selector switch for preventing the return of the line switch to normal after the selector switch has been seized, and means for rendering the last named means ineffective should the subscriber replace his receiver before seizure of said selector "switch, whereby said line switch will be returned tonormal.

22. In a telephone exchange system, a telephone line, a line switch connected thereto and automatically operated to seize an idle trunk upon initiation of a call, a selector switch to which said idle'trunk is connected, means at said selector switch for preventing return of the line switch to normal after the selector switch has been seized, means actuated upon the seizure of said selector switch for stepping the same from normal should a subscriber replace his receiver before seizure of said selector switch, and means for further operating said'selector switch to again return the same to normal whereby the means for preventing return of said line switch to normal will be rendered ineffective. I I

V 23. In a telephone exchange. system, a telephone line, a selector switch having a definite normal position, a line switch connected tosaid line and operable to extend the same to said selector switch, said line switch also having a definite normal position, means for moving said selector switch from its normal position should a subscriber replace his receiver before the selector switchhas been seized, and means for returning the selector switch to its normal position whereby said line switch is also returned to normal.

9A. Ina telephone exchange system, a

telephone line, a selector switch having a definite normal position, a line switch connected to said line and operable to extend same to said selector switch, said line switch also having a definite normal position, electromagnetic'means at saidselector switch for moving the same from its normal position should a subscriber replace his receiver before the selector switch has been seized, and means for returning the selector switch to its normal position wvhereby the line switch is also returned to normal.

In witness whereof, I'hereunto subscribe my name this'17th day of August, A. D.

IVINFRED T. POWELL. 

